An angle of rotation sensor is known from German Patent DE 197 47 753 C1. Here, a magnetic field sensor generates sinusoidal and cosinusoidal electrical output signals as a function of the relative rotary position between a magnet attached to a rotating shaft and the sensor. Similar angle of rotation sensors are also known from German Patents DE 195 39 134 A1, DE 44 22 868 A1, DE 41 00 666 A1, and DE 43 01 704 A1.
However, these sensors can detect only an angular range of 0° to 360°, which is insufficient for many application purposes.
German Patents DE 195 06 938 A1, DE 197 39 823 A1, and DE 199 62 241 A1 therefore propose to expand the measurement range to more than 360° and to couple two sensors by means of gears to the shaft whose angle is to be measured, where the gears have different numbers of teeth. In a similar way, European Patent EP 0 386 334 B1 also proposes coupling two continuous potentiometers to the shaft by means of gears with different numbers of teeth. In these cases, the mechanical complexity of the gears is relatively high. In addition, flank errors and play in the gears cause measuring inaccuracies.
German Patent DE 101 40 710 A1 proposes the use of two sensors, one of which has a narrow first angle of rotation measurement range and the other a comparatively larger second angle of rotation measurement range. Here, the first sensor is highly precise and generates a precise linear output signal, while the second sensor is less precise and supplies merely a secondary signal, which is used to determine the period of the output signal of the first sensor. However, expansion of the measurement range beyond 360° requires a translation gear.
German Patent DE 198 13 569 A1 proposes providing a worm with spiral raised sections on the rotating shaft whose angle is to be measured, and attaching a sensor with a magnet opposite these raised sections. During rotation, the shaft displaces these raised sections linearly according to the pitch of the worm, whereby the sensor, namely a Hall element, measures the change inductance as a function of position relative to the raised sections of the worm. German Patents DE 299 14 310 U1, DE 44 37 939 C2, AT 004 639 U1, DE 39 35 261 A1, JP 11211456 A, JP 61283801 A, and DE 37 03 591 C2 thereby suggest converting the rotational motion of the shaft into an axial relative displacement between shaft and sensor.
U.S. Pat. No. 6,411,082 B2 shows an angle of rotation sensor with a magnetic field-sensitive sensor, such as a Hall element, which is mounted stationary in a housing, and with a permanent magnet, which can move linearly relative to the Hall element. The magnet is coupled to a rack, which converts the rotational motion between itself and the housing into a linear motion. The axial distance between magnet and sensor changes according to the rotary position. Since the pitch of the rack is known, a measure of the angle of rotation can be determined from the output signal of the sensor.
However, the latter sensors have less resolving power and thus measuring accuracy than the angle of rotation sensors mentioned in the introduction, which work with sinusoidal and cosinusoidal signals in the measurement range of 0° to 360°.